Compressor regulator



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INVENTORv Ca'l'lwffef:

H15 ATTORNEY.

Reuued Jan. 23, 1940 UNITED STATES PATENT OFFICE I COMPRESSOR REGULATORCharles 8. Baker, Corning, Y., assigner to Ingersoll-Band Company,Jersey City, N. J., a corporation of New Jersey Original No. 2,171,286,dted August 29, 1939, Se-

rial No. 190,799, February 16, 1938.

Application for reissue November 22, 1939, Serial No.

Claims.

This invention relates to motor driven iiuid compressors, and, moreparticularly, to apparatus to control the speed of the motor by thevariations in the discharge pressure of the compressor and to maintainthe compressor fully loaded until the speed of the motor has beenreduced to a minimum.

A motor driven iiuid compressor unit comprises a motor or engine, suchas an internal combustion motor or steam engine, directly connected todrive a compressor which compresses a uid and delivers it to a receivertank where it is stored until used. Ordinarily, in order to preventoverloading of the receiver, regulator means are provided which, whenthe pressure in the receiver tankreaches a predetermined point, operatesto prevent a further discharge of fluid to the receiver from thecompressor (commonly termed unloading) and, at the same time, reducesthe speed of the motor to a minimum or idling speed. The compressor unitthen idles until the pressure in the receiver tank falls to apredetermined minimum pressure whereupon the regulator operates topermit the compressor to discharge fluid to the receiver tank (commonlytermed re1oading) and to accelerate the motor to its maximum operatingspeed.

'I'he disadvantages of operating the compressor unit in this way arethat the compressor will not run at a minimum speed at any time unlessthe compressor is completely unloaded, nor will it operate at any speedbut the maximum speed when the compressor is loaded.

It is, accordingly, an object of the present invention to provide meanswhereby the Speed of the motor of a compressor unit may be controlled byvariation in the discharge pressure of the compressor.

It is another object of the invention to provide` means whereby a motordriven compressor unit may operate at its minimum speed withoutunloading.

It is a further object to 'provide means in a compressor unit wherebythe compressor may be gradually unloaded in accordance with a gradualrise in the discharge pressure of the compressor after a predeterminedhigh discharge pressure of the compressor is reached.

Still another obiect is to provide means in a compressor unit wherebythe degree of unloading or reloading of the compressor is dependent onthe discharge pressure of the compressor.

A further object is to provide a device in a compressor unit whereby themotor speed is held at a (ci. 23o- 4) minimum during unloading andreloading of the compressor.

Still another object is to provide a device in a compressor unit wherebythe motor may accelerate or decelerate between the maximum and theminimum speeds of the motor before the compressor begins to unload.

Another object is to provide a compressor unit with a device whereby themotor may be accelerated anddecelerated between its maximum and minimumspeeds until the compressor discharge pressure reaches a predeterminedhigh pressure and thereafter remain at its minimum speed until apredetermined minimum discharge pressure is reached.

These and further objects will be readily apparent from the followingdescription of which the drawings, in which similar numerals indicatelike parts, form a part and in which Figure 1 is a view partly inelevation and partly in section illustrating the application of thepresent invention to a compressor unit. A portion of the governorregulator and the governor is increased in size in order that thedetails may be brought out more clearly,

Figure 2 is a view partially in elevation and partially in section ofthe governor regulating portion of the regulator constructed in accordance with the principles of this invention, and

Figure 3 is a view similar to Figure 1 illustrating the application of amodification of the present invention to a compressor unit.

Figure 4 is a sectional view of the governor regulator illustrated inFigure 3, and

Aand directly connected to drive the fluid cornpressor-T, which islikewise mounted on the frame 3. Fluid is delivered to the compressor 1througha conduit 9 and delivered from the compressor to a receiver tankI I by the conduit I3.

Thev speed of the motor i is controlled by a governor generallyindicated at I5, having a shaft I1 directly connected to the shaft ofthe /motor I (not shown).` The shaft I1 has a flange I9 to which issecured a gear 2|. Fulcrumed at 2l, onthe gear 2 I are weights 25 whichcarry rollers 21.

Accordingly, when the Weights move outwardly against the force of thegovernor spring 33, the motion of the plate 29 is transmitted throughthe ward the left the consequent anti-friction bearing 35 to a plate 31formed integral with pin 3| coaxial with and slidably mounted on theshaft I1. The plate 31, through the clevis 39 and a lever 4I, fulcrumedon the frame of the motor at 43, transmits motion to a link 45 rotatablyconnected to the lever 4|, by pin 41 at the end opposite to that atwhich the olevis 39 is secured. This tie-rod or link 45 actuates thebutterfly valve 49 in the fuel intake of the motor I, and since outwardmovement of the weights 25 will cause the tie-rod 45 to move tomovementof the butterfly valve will vdecrease the fuel supply to the motor andthus ydecelerate the motor speed. Thus, as the motor I rotates,centrifugal force causes the weights 25 to fly toward their outermostposition and upon reaching this position they cause the closing of thethrottle valve 4,9

- to prevent a further increase in the speed of the motor.

Conversely, as the speed of the motor is`decreased, the weights 25 movein towards the shaft I1 causing the plate 23 to move in the samedirection and pivot the lever 4| about its fulcrum '43. This makes thetie-rod 45 pivot the butterfly valve about its fulcrum 5I toward itsopen position to increase the fuel supply to the motor and to thus tendto accelerate'the speed of the motor.

As is customary in centrifugal governors, the weights 25 are held intheir retracted position by the governor spring 33 and the tension ofthis spring determines the motor speed at which the weights 25 will moveto their outermost position. In order to house the spring, a casing 53having a bore 55 extending therethrough is secured on the frame of themotor. The bore 55 communicates with a recess 51, formed in one end ofthe casing 53, and has a plunger 59, provided with a flange 6| restingin the recess 51, extending therethrough. One end of the spring 33 restsagainst the flange 3| and the opposite end bears on member 53 and holdsthat member against a projection 65 provided on the lever'4I.

The portion of the plunger 59 which extends outside of the casing 53bears against a. hooked lever 61, fulcrumed on the casing 53 at 33 andadapted to move the plunger-59 to compress or release the spring 33.Since the speed setting of the governor is determined by the amount offorce the weights 25 must exert on the plate 29 in order to overcome theforce of the spring 33, it is apparent that, should the hooked lever 51force the plunger 59 to compress the spring 33 to its compression limit,the motor will have to operate at its maximum speed in order that thecentrifugal force of the weights 25 Shall be sufficient to overcome theresistance of the spring 33. Under such conditions, consequently, inorder for the weights to move outwardly enough to move the lever 4| tothrottle the motor, the speed of the motor must exceed the maximumdesired speed. f

Conversely, if the hooked lever 51 is moved in the opposite direction,so that the spring 33 may expand, plate 29 may be moved out from theshaft I1, by the weights 25when the motor is operating at a much slowerrate. As a result, under such circumstances, the motor will operate at aminimum speed and the slightest increase in speed will cause the weights25 to move the plate 29 further away from the shaft and thereby furtherclose the butterfly valve to throttle the motor intake and decrease thespeed to the desired minimum motor operating speed.

It follows, therefore, that, if the position of the hooked lever 21 iscontrolled, the speed setting of the governor may be changed to regulatethe motor speed in varying degrees and for that purpose a pressureresponsive device which will assume various positions in accordance withthe discharge pressure of the compressor is connected to the lever 31 bya tie-rod 1 I.

The details of the regulating mechanism are best illustrated in Fig. 2.With reference thereto it will be noted that it consists of a casinggenerally indicated at 12 secured to the motor frame by suitable meanssuch as the bolts 13 and provided with a bellows chamber 14 closed by ahead 15. The interior ofthe bellows chamber 14 is connected directly tothe receiver tank by a conduit 13.A The conduit 13 threadedly engagesthebushing 11 which has an orifice 18 to restrict the iiow of uid comingfrom the receiver. The fluid enters the bellows chamber 14 after leavingthe orilce 13 through the passage 19.

Head 15 is provided with a passage 33 through which extends the plungerrod 3|, having a piston member 32 fastened to the end thereof wthin thebellows chamber. One end of a bellows 33 v is secured to the piston 32in air-tight relationship and the opposite end of the bellows is securedin air-tight relationship between the casing 12 and the head 15 in orderthat it will be impossible for any fluid in the bellows chamber 14 toenter the bellows proper 83.

At the opposite side of the casing, to that where orifice 18 ispositioned, is a passage 84 passing through a portion of the casing 12and the head 15. In this passage is a bushing 35 with an orice 33secured in an end thereof. The area of the orifice 83 is larger than thearea of the orice 13 and, consequently, the fluid entering' the bellowschamber is restricted more than the fluid leaving the bellows chamberthrough orifice 33. l

With this arrangement of parts the bellows chamber wil be subjected tofluid at the same pressure as the fluid in the receiver tank since fluidis conveyed from the receiver tank to the bellows chamber by the conduit16 and enters the chamber through the orifice 18. If the orifice 88 werenot provided, it is readily apparent that the bellows chamber 14 wouldconstantly be subjected to the same pressure as the receiver II.However, with a means, which will be described hereinafter, to open andclose the venting orifice 86 the pressure in the bellows chamber 14 willvary considerablyv from the pressure in the receiver tank II.

The external end of the plunger rod 3| is clevised and rotatablyfastened to the lever 31 by the pin 83 which also serves to connect theregulator lever 39, fulcrumed at 98, on the head 15. The pin 38 thusmakes it possible to have relative rotation between the levers 81 and 89and the plunger 8|. Surrounding this pin conneotion is a guard 3| formedas a part of the head 15 threadedly engaged by the bolt 92,1ocked inposition by the lock nut 93. to regulate the outward movement of theplunger 8|.

VAs a result of this arrangement, when orifice 86 is closed, thepressure in the bellows chamber 14 corresponds to the pressure in thereceiver tank II, and if the pressure is sumcient, it will move thebellows 83 to the right. This movement will be opposed by the resilienceof the bellows 83 and the pressure of atmosphere, since passage 80 islarge enough to permit air to enter around annee it will allow theplunger 8| to move to the rightalso andmovement will cease only when theend of the plunger 8| bears against the bolt 82.

Conversely, when the orifice 8l is opened, the pressure in the bellowschamber 14 will drop since fluid may escape to atmosphere permitting theresilience of the bellows 88 and atmospheric pressure to move thebellows tothe left carrying the plunger 8| with it.

Movement of the plunger 8| will pivot lever 89 about its fulcrum 90 andthus, by means of tie-rod 1|, transmit movement of the bellows 88 intoregulation of the compression on governor spring 33.

The apparatus controlling the opening and closing of orifice 88 will nowbe described. In the upper part of the casing 12 is a recess 94 havingan enlarged portion 95 in which is secured, by plate 96, suitablyfastened to the casing, a diaphragm 91. A branch of conduit 15 issccured in the passage 98 opening into the dia.- phragm chamber 99. Itwill thus be seen that the receiver tank pressure will be maintained inthe diaphragm chamber 99. At the casing end of recess 94 is a threadedbore |00 designed to receive the guide bushing I0| for the plunger |02extending into the recess.

'Ihe plunger |02 has a follower portion |03 bearing against thediaphragm 91. Within the recess 94 the guide bushing |0| has a flange|04 on which one end of a spring |05 rests and the opposite endjof thespring bears against the follower l03. By means of the guide bushing I0I the compression of the spring |05 may be vregulated and a lock nut|08 serves to maintain the bushing in a fixed position.4

The end of the plunger |02 opposite to the end having the follower |03is reduced in diameter ,and has a threaded portion I 01 to receive aregulating bushing |08 and a locking means such as the nut |09. rTheupper portion of lever 81 is provided with a passage ||0 of sumcientdiameter to permit the shaft |02 to pass therethrough.

A spring is maintained between the lever 81 and the bushing |08. Wherethe reduced portion of the shaft |02 begins a shoulder is formed andwhichprovides a seat for the slldable abutment I I2. 'I'his slldableabutment is freely movable on the reduced portion of the shaft |02. Thespring II normally holds the lever 81 against the abutment ||2. In orderto permit free movement of the lever 81 about pin 88 and a constantcontact point between that lever and abutment ||2, a recessed surface||3 is formed on the lever 81 to prevent the tip end of the lever fromtouching the abutment. `Intermediately placed on 'the lever 81 is abutton valve ||4 which is so positioned with respect to the orifice 85in the bushing 85 that, under normal conditions, the button obstructsthe orifice and at least to some degree prevents escape of fluid fromthe bellows chamber 14.

In order to lock the apparatus in the maximum speed setting position, alocking cam and handle I I5 is pivotally mounted on the head 15 and maybe moved into position to lock the lever 89 in a position to maintainthe maximum tension on the governor spring 33.

From this description it will be seen that, as the pressure in thereceiver tank increases, the pressure on diaphragm 91 will increase,tending lto move the diaphragm and shaft |02 toward the right againstthe resistance of spring |05. As shaft |02 moves to the right, it pushesabutment II2 against the end of lever 81 which, consequently movesrightwardly. Only the upper portion of lever 81 will move since thelower end pivots about pin 88 and, consequently, the button valve ||4 ismoved away from orifice 88 to open that orifice. On the other hand,assuming that orifice 86 is open, due to a high pressure in the receivertank, and that the pressure begins to fall, Ithe diaphragm 91, andspring I will be moved leftwardly when the compression of spring |05 issufncient to overcome the pressure of the fluid in diaphragm chamber 98.This movement will pivot lever 81 toward the left and thereby closeorifice 85.

In the modified regulator illustrated in Figs. 3 and 4 the parts and theoperation is slightly `different and it will be seen to consist of acasling IIE securely fastened to the frame of the motor by suitablemeans such as the bolts I1.

The casing 8 is provided with a bellows chamber ||8, closed by a headH9, communicating with the intake manifold |20 of the motor through theopening I2I, in which is secured a bushing |22, having an orifice |23,to connect the pipe |24, leading from the intake |20 of the motor, tothis chamber. Within the chamber ||8 and bearing against a wall thereofis a spring |25, the other end of which bears against the member |25,provided with a flange |21, forming the head of the bellows |28 and towhich one end of the bellows is secured. The other end of the bellows isheld between the casing |I8 and the head ||9.

Centrally located in the head I9 is a bore |29 through which extends ahollow shaft |30 secured to the member |26 and providing communicationwith the passage |3| in the member |26. A bushing |32 having an orifice|33, is inserted in the passage through shaft I 30 which vents thechamber ||8 to the atmosphere.

It will thus be apparent that, while the motor is operating, the vacuumset up in the intake manifold is directly communicated to the bellowschamber I|8 through the conduit |24, the orifice |23 and the opening 2|.If there were no vent for this chamber, the vacuum set up therein wouldcause-the bellows to expand against the compressive force of the spring|25. However, since the evacuation of air from the bellows chamber ||8is restricted by the orifice |23, a vacuum cannot be effected in thatchamber unless the orifice |33 is at least partially closed. Thus, withthis orifice |33 open, air may enter through the orifice |33 and passthrough the shaft |30 and the member |26 into the casing and be drawnthrough the conduit |24 to the intake manifold |20.

The shaft |30 carries an extension clevis |34 to which is fastened, bythe stud |35, the lever I 38 fulcrumed on a portion of the head 9, at|31, and rotatably secured to the tie-rod 1 I. seen that movement of thebellows under the ihfluence of the vacuum in chamber 8 will be directlytransmitted to the governor spring 33. The range of longitudinalmovement of the shaft |30 is limited by the position of bolt |64threadedly engaged in the head ||9. Movement of the bellows 28 andtheshaft I 30 is controlled by regulating the degree of the vacuum set upin the chamber I8. .Such regulation is accomplished by the T-lever |38fulcrumed at |39 and adapted to control the orifice |33.

The movement of the lever |38 is controlled by the pressure responsivedevice generally indicated at |40. This device consists of plunger I4Ishaft |02, bushing |08 n will be having a head |42 and adapted to beactuated by a diaphragm |43 against which it is held by the pressure ofa coil spring |44. Plunger |4| is guided in va sleeve |45 extending intochamber |46 formed in casing II6, and threaded therein being held inplace by lock nut |41. Diaphragm |43 is held in place by a head |48bolted to ange |49 of casing II6 and forming a pressure chamber II|, theinlet |5I of which is connected by means of pipe |52 to the receivertank Spring |44 bears against the `head |42 of plunger |4| i and flange|53 on bushing |45, its tension being adjustable by screwing the bushinginto or out of the chamber |48, suitable flats |54 being provided forthat purpose on the bushing |45.

A part |55 of the shaft |44, which extends outside of the casing ||8 andsleeve |45, is reduced in diameter and is provided with a bearing flange|56 of greater diameter than the shaft |4I proper. Slidable member |51supported by this part |55 of the shaft and bearing against the spring|58 is held on the shaft by a nut |59, whichv also serves to regulatethe degree of compression on the spring |58. Leg |88 of lever |38 isinterposed between bearing flange provided with a hole IBI to receiveportion |55 of plunger |4I. The motion of plunger |4| is thustransmitted to tionat the opening of orifice |33.' One portion of themember |51 rests on the raised portion |82 provided on the leg |83 ofthe T-lever |38 and is arranged to latch therewith as will be describedhereinafter.

With reference again to Figs. l and 3, a means to unload and reload thecompressor is provided between conduit 9 and the compressor 1. Thedetails of this device are illustrated in Fig. 5 and consist of a casing|85 connected to the conduit 9. A portion of the walls of the casingextend within the outer walls thereof to form the valve guides |61 lforthe balanced cylindrical valve |69. An opening |1| in the casing isclosed by a plate |13 which is provided with a recess |15 wherein aspring |11 rests. This spring normally urges the cylindrical valvetoward its right hand or open position. When the valve is in its openposition, the fluid may enter from conduit 9, flow past the cylindricalvalve |69 and into the compressor.

Another chambered casing |19 is secured on one side of the casing |85directly opposite to the plate |13. In this chamber casing is the guide|8| formed integrally with the chamber casing |55 to slidably support abushing |83` which,'in turn, supports the rod |85. One end ofthe rodbears against the cylindrical valve |69 and has a head |81 formed at theopposite end thereof.

The head |81 rests against a diaphragm |89 which is secured to thechamber casing |19 by the cup |9|. AThe bushing |83 is formed with aflange |93 to bear against the spring |95. normally urging the head |81andshaft |85 toward the right. Between the diaphragm and the cup |9|, isa chamber |91 which is in direct communication with the receiver tankthrough the conduit |99. With this device forming part of the compressorunit it will be noted-that, as the pressure in the receiver tankincreases to the point where itis sufficient to move the head 81 againstthe. compression of the spring |95, the rod |85 will move to the lefthand, consequently, move the cylindrical valve toward its closedposition. If therpressure should decrease after reaching this point, thespring will move the rod |85 toward the right against the pressure inthe re- |56 and spring |58 being lever |38 to vary the restric-,

ceiver'and the cylindrical valve will follow the rod |85, being urged bythe spring |11.

Ihe operation of the invention described above is as follows: y

Referring again to the regulator shown in Figs.

1 and 2 and assuming that the pressure in the 1 receiver is below adesired minimum value, lack of vpressure in the chamber 89 permits thespring |85 to maintain the diaphragm 91 and the shaft |82 in its leftvhand position (Fig. 2). In that position the spring against theabutment |2 thus holding the button valve ||4 against the orifice 88 toprevent the will hold the lever 81 escape of fluid through the oricefrom the chamv ber 14. With this orifice closed, the pressure in chamber14 will naturally be the same as the' pressure existing in the receivertank Upon increasing the pressure in the chamber 14 the bellows 83 willcollapse causing plunger 8| to exert force on lever 89 which, throughlink 1|, lever 61 and plunger 59, compresses the governor spring 38tending to open the throttle valve 49. In this manner the speed settingof the governor |5 is changed t'o increase the speed of engine I. As themotor speeds up, the pressure in the receiver tank begins to rise and toincrease the pressure on diaphragm 91. Shaft |82 thus pushes against theabutment Il! which,

in turn, moves the lever 81 until the button valve I4 begins to open theorifice 86. Fluid may then escape faster from chamber 14 through thelarger orifice 86 than it enters the chamber through the smaller orice18. Atmosphereic pressure within the bellows 93 then tends to expand thebellows and to withdraw shaft 8| into the bellows pulling with it lever89 and correspondingly reducing the compression of governor spring 33,closing the throttle valve 48, and reducing the engine speed. Thereduction in engine speed correspondingly reduces the rate oi increaseof compressor discharge pressure at receiver As the discharge pressurecontinues to increase, plunger |82 continues to push against lever 81 soas to maintain orifice 88 open.

The above described interaction continues until the motor speed isreduced to a point at which the compressor produces just enough air tosupply the demand or until the discharge pressure reaches apredetermined value whereat the motor is reduced to its minimum speed.Prior to reaching such predetermined pressure the diaphragm 91 andplunger |02 will have reached their extreme right hand position wherethey remain so long as the pressure in the receiver does not fall.

Upon reaching the predetermined high pressure above referred to, thecompressor is further unloaded progressively by choking its inlet. Thisis accomplished by apparatus shown in detail in Fig. 5. The initialcompression of the spring |95 is adjusted by means of the threadedbushing |83 to equal the total pressure on the opposite side ofdiaphragm |89 when the above mentioned predetermined high pressure isreached. At values above that pressure, diaphragm |89 pushes the plunger|85 against inlet valves |69 to overcome compression of the spring |11;thus, the openings at |61 become more or less restricted to unload thecompressor 1 in a degree corresponding to the pressure existing in thereceiver while the speed of motor remains at its minimum. At somepredetermined high pressure it will be seen that the valve |89 willcompletely choke the compressor inlet and thereby completely unload thecompressor. Upon resnm t and plunger |4| moves to the right, the portionduction oi' discharge pressure, the compressor will be completelyreloaded inasmuch as the valve will beat its open-most position.

The speerl of the engine I will be resumed i! the discharge pressurecontinues to fall. During auch lowering of pressure, plunger |02 iswithdrawn into the chamber 84 with consequent change in the position oflever 01 to thereby permit the button valve I4 to close the oriilce 00.The spring |00 will hold the plunger |02 in the withdrawn position untilthe pressure in the receiver tank increases whereupon the same cyclewill occur.

Obviously, under varied loads, the regulator may accelerate orvdecelerate the engine without approaching the minimum or maximum speedsoi the engine I. Furthermore, the pressure in the spring |00 may beadjusted to predetermine the pressure necessary to 4move the plunger |02and by this means the minimum and maximum speeds may be predetermined.

'I'he operation oi the regulatoroi' Figs. 3 and 4 is as follows:

Assuming that the-pressure in the receiver is below a desired minimumvalue, a lack oi' pressure in the chamber |00 permits the spring |44 tomove the diaphragm |43 and the shaft 4| to the left (Fig. 4). In thatposition the lug |01 has passed beyond the raised portion i 02 and restsin the recess |08 formed on the leg |03 of the T-lever.|38. The T-lever|38 is held out of engagagement with the orifice bushing |32 and permitsthe entry oi air through the orifice and shaft to the chamber H8.Atmospheric pressure in chamber ||8 equalizes the fluid pressure onbellows and permits spring |25 to collapse the bellows and exert forceon lever |38 which, throughlink 1|, lever 01 and plunger 58, compressesgovernor spring 33 tending to open throttle valve 40. In this manner thespeed setting of the governor |0 is changed to increase the speed ofengine As the motor speeds up, the pressure in the receiver tank beginsto rise and to increase the pressure on diaphragm |43. Plunger |4| thuspushes against the end |00 of lever |38 until the other end of thatlever begins to restrict the orifice in bushing |32. Air is thenwithdrawn from chamber through the larger orifice |23 than it enters thesmaller orlilce |32. Atmospheric pressure within bellows |28 opposes thespring |25 and the shaft |20 tends to withdraw from lever |38 pullingwith it lever |30 and correspondingly reducing the compression ofgovernor spring 33, closing thethrottle valve 4, and reducing the enginespeed. The reduction in engine speed also reduces the rate of increaseof compressor discharge pressure at receiver As the discharge pressurecontinues to increase, plunger |4| continues to push against lever |30so as to close the oriilce |33 and, simultaneously, the unbalance of airpressure on bellows |20 tends to withdraw that orifice from the leverwith the consequent adjustment of compression of governor spring 33causing reduction in the motor speed. The above described interactioncontinues until the motor speed is reduced to a point at which thecompressor produces just enough air to supply the demand or until thedischarge pressure reaches a predetermined value whereat the motor isreduced toits minimum speed also.

Prior to reaching such predetermined pressure, the sliding flange |01has been hooked behind the projection |02. As the pressure increases ||0faster-- o! lever |30 designatedby |00 also moves to the right. Thismovement causes projection |02 to move d own until sliding ilange |01over-rides projection |02 and flange |01 is pushed ahead by spring 00 tolock lever |30 in place. 'I'he pressure responsive devices includinglever |30 and bellows |28 and thexdevices actuating and actuated by themare rendered inoperative until a predetermined low discharge pressure isreached as will be described hereinafter.

The unloading device of Fig. 5 operates with this regulator in the samemanner, as described in connection with the regulator of Figs. 1 and 2.Thus, after unloading the compressor and reloading the compressor', thespeed of the engine will not be resumed until the lowest permissibledischarge pressure is reached, due to the latching of the plunger |01 onthe projection |02 of lever |30 (Fig. 4). During such lowering oipressure, plunger |4| is withdrawn into chamber |46 without change inthe position of lever |30, keeping closed the orifice |33 until nut |00withdraws ilange |01 from engagement with projection |02. Spring |00 iscompressed during such withdrawal and, upon the disengagement re- Ierredto, causes.end |00 of lever |30 to resume its position against theabutment |00, whereupon ilange |01 drops into the recess |05.Correspondingly, the end of lever |30 moves out of engagement with theorice |33 to admit atmos pheric pressure into bellows |28. Thereupon,the movement of plunger |4|, under the inuence of pressure in chamber|00, resumes control of the movement of the lever |30 and governorspring 33 as described above.

`It will be seen that adjustment of the sleeve |40 in the casing iseiected by turning the nut |04 and has the effect of moving the button|00 longitudinally with regard to the housing and, correspondingly,moves the end of lever |30. By this means, therefore, can be adjustedthe pressure at which speed of the motor begins to be eiected. Likewise.adjustment of the sliding flange |51 with respect to the plunger |4|,which is eiected by adjustment of nut |59, will effect the low pressureat which plunger |51 disengages itself from the projection |02. Themaximum speed of the motor may also be determined by adjustment of thestop screw |04 which limits the movement of lever |38 (Fig, 4).

If, for example, the motor is to be operated at its minimum speed whenthe pressure in the receiver tank has reached pounds per square inch,the compression of spring |00 is so adjusted in the regulator of Fig. 2Vthat lever 01 will hold valve i |4 in position to prevent the escape offluid from chamber 14 and likewise the compression oi' the spring |44 ofthe regulator of Fig. 4 is so adjusted that the lever |30 will prevententrance of air into the chamber ||8 to thus reduce the motor speed tothe minimum when that pressure is reached. It the pressure at which theunloading device is to begin functioning is pounds per square inch, theproper compression on the spring |05 is secured by regulation of thebushing |83, and when pressure increases to that pressure the unloadingdevice will come into action and will gradually close the cylindricalvalve. If the pressure increases still more until it reaches thepressure atwhich the compressor is 'to be completely unloaded, namely,at 105 pounds per square inch, the compressor will be completelyunloaded. As long as the pressure in the receiver remains within therange oi 100 to 100 pounds per square inch. the cylindrical valve willassume a closed or partly closed position ccmparablewith the pressure inthe receiver tank. II, however, the pressure in the receiver tank fallsbelow 100 pounds per square inch, the spring |95 Vwill overcome thepressure in the receiver tank and maintain the cylindrical valve open.Should the pressure continue to tall because of a heavy load, thegovernor regulator of Fig. 2.will begin to accelerate the motor towardsits maximum speed as soon as the pressure falls below 95 pounds pressureand will thenceforth control the speed of the engine whereas theregulator of Fig. 4 will continue to maintain the motor at its minimumspeed until some pressure such as 80 pounds per square inch is reachedat which time the lever |38 will be free from the oriilce as wasexplained previously and the motor may again accelerate to its maximumspeed.

It is manifest, therefore, that the unloading and reloading device willnot operate until a pressure is vreached suillcient to maintain thegovernor at a minimum speed setting position and will then vary thedegree of loading oi the compressor in accordance with variations in thedischarge pressure of the compressor. Furthermore, when the pressurefalls, the governor speed regulator of Fig. 2 will begin regulating themotor speed as soon as the compressor is completely reloaded whereas theregulator oi Fig. 4 will maintain the motor at its minimum speed until amuch lower pressure than that required to obtain minimum speed isreached.

The pressures herein designated have been assumed merely for rthe sakeof explanation and may be varied to secure other speed and unloadingranges provided the unloading device does not begin to function untilthe motor is operating at substantially its minimum speed. Furthermore.it may be advantageous to operate the compressor unit in a manner topermit the compressor to begin unloading at the same pressure as that atwhich the speed of the motor is reduced to its minimum speed.

During the operation of the compressor under the above pressure settingsand under loads which prevent the receiver pressure from increasing to95 pounds per square inch, the motor speed will progressively anddegressively vary as the pressure in the receiver increases anddecreases. Thus, if the 'pressure in the receiver increases anddecreases, the motor speed will increase and decrease inversely with thepressure changes. Of course, with the regulator of Fig. 4, after thepressure reaches95 pounds per square inch, this regulator maintains thespeed at the minimum speed until vthe pressure in the receiver decreasesto the predetermined low pressure, namely 80 pounds per square inch, atwhich point the compressor will begin reloading at maximum speed again.

Likewise, when the pressure in the receiver hovers within the range of100 to 105 pounds per square inch, the degree of unloading or reloadingvaries progressively and degressively with the pressure change. Thus, ata pressure in close proximity to 105 pounds per square inch, thecompressor will be almost completely unloaded whereas, with the pressureabove but in close proximity to 100 pounds per square inch, thecompressor will be almost completely reloaded. Within this range theamount which the unloading valve opens and closes depends on thepressurein the receiver tank and will vary the pressure. Upon an increase inpressure, the

with the variations oi'. y

valve will close and.A upon a decrease in pressure,

it will open.

It is understood that the constructions above described. are preferredembodiments oi the in-` vention and that many changes which do notdepart from the scope and spirit oi' the invention will occur to thoseskilled in the art.

I claim:

1. In a motor driven iiuid compressor unit having a motor speedgovernor, a pressure responsive regulator to control and vary the speedsetting oi the governor upon variation or the discharge pressure of thecompressor below a predetermined high discharge pressure. and means tovary the quantity of fluid admitted to the compressor between a maximumand a minimum quantity upon any variation in the discharge pressure ofthe compressor above said predetermined high discharge pressure.

2. In a motor driven iluid compressor unit having a motor speedgovernor, a pressure responsive regulator to control and vary the speedsetting of the governor between maximum and minimum motor speed upon anyvariation of the discharge pressure respectively between a predeterminedminimum discharge pressure and a predetermined high discharge pressureof the compressor. and means to vary the quantity of iluid admitted tothe compressor between a maximum and a minimum quantity upon anyvariation in the discharge pressure respectively between saidpredetermined high discharge pressure and a predetermined maximumdischarge pressure or the compressor.

3.` In a motor driven fluid compressor unit having a motor speedgovernor, a pressure responsive regulator to control and vary the speedsetting of the governor having speed setting positions between maximumand minimum motor speed, means to control the pressure responsiveregulator and vary its speed setting position upon any variation in thedischarge pressure of the compressor between a predetermined minimumdischarge pressure and a predetermined high discharge pressure, andmeans to vary the quantity of fluid admitted to the compressor uponvariation in the discharge pressure of the compressor above saidpredetermined high discharge pressure.

4. In a motor driven huid compressor unit having a motor speed governor,pressure responsive means having positions intermediate the maximum andminimum motor speeds to control and vary the speed setting of thegovernor, means to control the pressure responsive means and vary itsspeed setting position between maximum and minimum motor speeds uponrespective variations intermediate a predetermined minimum dischargepressure and a predetermined high discharge pressure of the compressor,and means to varyV the quantity of fluid admitted to the compressorbetween a maximum and a minimum quantity upon any variation in thedischarge pressure of the compressor respectively between saidpredeterminedhigh discharge pressure and a predetermined maximumdischarge pressure of the compressor.

5. In a motor driven fluid compressor unit having a motor speedgovernor, pressure responsive means to control and vary the speedsetting of the governor upon variation of the discharge pressure oi thecompressor below a predetermined high discharge pressure comprising acasing having a chamber, means in the chamber subject to the dischargepressure oi the compressor adapted charge pressure in said secondchamber to open Y and close said vent, and means to vary the quantity offluid admitted to the compressor upon any l variation in the dischargepressure of the compressor above said predetermined high dischargepressure of the compressor.

6. In a motordriven fluid compressor unit having a speed settinggovernor to regulate the speed of the motor, a pressure responsivedevice to control and vary the speed setting of the governor uponvariation of the discharge pressure of the compressor below apredetermined high discharge pressure and having a maximum and minimumspeed setting position, means forming a part of said device to cause thepressure responsive device to gradually change the speed setting of thegovernor to the minimum speed position as the discharge pressureapproaches said predetermined high discharge pressure, and means to varythe quantity of fluid` admitted to the compressor upon any variation inthe discharge pressure of the compressor between said predetermineddischarge pressure and a predetermined maximum pressure.

'1. In a motor driven fluid' compressor unit having a speed settinggovernor to regulate the speed of the motor, a pressure responsivedevice to control and vary the speed setting of the governor uponvariation ofthe discharge pressure of the compressor below apredetermined high pressure, means to predetermine said high pressure,and means to vary the quantity of fluid admitted to the compressor uponany variation in the discharge pressure above said predetermined highdischarge pressure. n

8. In a motor driven fluid compressor unit having a speed settinggovernor to regulate the speed of the motor, a pressure responsivedevice to control and vary the speed setting of the governor betweenmaximum yand minimum motor speed positions upon any variation of thedischarge pressure respectively between a predetermined minimumdischarge pressure and a predetermined high discharge pressure oi' thecompressor, means to predetennine said minimum and high dischargepressures, means to vary the quantity of fluid admitted to thecompressor between a maximum and a minimum quantity upon any,1 variationin the discharge pressure respectively between said predetermined highdischarge pressure and a predetermined maximum discharge pressure of thecompressor, and means to predetermine said high and maximum pressureswith respect to the last said means.

9. In a motor driven fluid compressor unit having a speed settinggovernor to regulate the speed of the motor, a pressure responsivedevice to control and vary the speed setting of the governor uponvariation of the discharge pressure of the compressor below apredetermined high 'discharge pressure, and means to vary'the quantityof fluid admitted to the compressor upon any variation in the dischargepressure of the compressor above said predetermined high dischargepressure comprising a casinghaving a chamber therein associated with thefluid inlet of the compressor, a valve in the fluid inlet of thecompressor, movable means subject to the discharge pressure of thecompressor in said chamber and connected to move said valve uponmovement thereof, and means to predetermine the pressure at which saidmovable means 'will move.

10. In a motor driven fluid compressor unit having a speed settinggovernor to regulate the speed of the motor, a pressure responsivedevice to control and vary the speed setting of the governor uponvariation of the discharge pressure oi' the compressor below apredetermined high discharge pressure and having various speed settingpositions between maximum and minimum speed setting position, meansforming a part of said device to cause the device to graduallychange'the speed setting oi the governor to the minimum speed positionas the discharge pressure approaches said predetermined high dischargepressure and to gradually change the speed setting of'the governor tothe maximumspeed position as the discharge pressure decreases from. saidpredetermined high discharge pressure toward a predetermined minimumdischarge pressure,

and means to vary the quantity of fluid admitted to the compressor uponany variation in the discharge pressure of the compressor between saidpredetermined high discharge pressure and a predetermined maximumpressure.

11. In a motor driven iiuid compressor unit having a speed settinggovernor to regulate the speed of the motor. a pressure responsivedevice to control and vary the speed setting of f the governor uponvariation of the discharge pressure of the compressor below apredetermined high discharge pressure and having various speed settingpositions between maximum and minimum speed setting position, meansforming a part of said device to cause the device to gradually changethe speed setting of the governor to the minimum speed position as thedischarge pressure approaches said predetermined high discharge pressureand to gradually change the speed set-y ting of the governor to themaximum speed position as the discharge pressure decreases from saidpredetermined high discharge pressure toward a predetermined minimumdischarge pressure, means to gradually reduce the quantity of fluidadmitted to the compressor to a minimum as the discharge prsureapproaches a predetermined maximum discharge pressure and to in' creasethe quantity of fluid admitted to the compressor to maximum as thedischarge pressure decreases from the predetermined maximum dischargepressure toward the predetermined high discharge pressure.

12. In a motor driven fluid compressor unit having a speed settinggovernor to regulate the speed of the motor, a pressure responsivedevice to control and vary the speed setting of the governor uponvariation of the` discharge pressure of the compressor below apredetermined high discharge pressure and having various speed settingpositions between maximum and minimum speed setting position, meansforming a part of said device to cause the device to gradually changethe speed setting of the governor to the minimum speed position as thedischarge pressure approaches said predetermined high discharge pressureand to gradually change the speed setting of the governor to the maximumspeed position as the discharge pressure decreases from saidpredetermined high discharge pressure toward a predetermined minimumdischarge pressure, and means to vary the quantity of fluid admitted to.the compressor upon any variation in the discharge pressure of thecompressor above said predetermined high discharge pressure comprising acasing having a chamber therein associated with the fluid inlet of thecompressor, a

valve in the iiuid inlet of the compressor, movable means subject to thedischarge pressure-ot the compressor in said chamber and connected tomove s aid ,valve upon movement thereof, and means to predetermine thepressure at whichsaid `movable means will move.

,13. In a motor driven fluid compressor unit` having a speed settinggovernor for the motor, a pressure responsive means to 'control and varythe speed setting of the governor upon variation of the dischargepressure of the compressor below a predetermined high discharge pressurecomprising a casing having a chamber, means in the chamber subject tothe discharge pressure oi the compressor adapted to regulate the speedsetting position of the governor, a vent for the chamber, a secondchamber in the casing subject to the discharge pressure of thecompressor, means to open and close said vent responsive to thedischarge pressure in said second chamber,

means to vary the quantity of iiuid` admitted to' the compressor uponany variation in the discharge pressure of the compressor above saidpredetermined highv discharge pressure comprising a casing having a,chamber therein associated with theiiuid inlet of the compressor, avalve in the iiuid inlet of the compressor, movable means subject to thedischarge pressure of the compressor in said chamber and connected tomove said valve upon movement thereof, and means to predetermine thepressure at which said movable means will move.

14. In a motor driven iluid compressor unit having a speed governor, apressure responsive device to control and vary the speed setting of thegovernor upon variation of the discharge pressure of the compressorbelow a predetermined high discharge pressure, means to gradually reducethe quantity of iiuid admitted to the compressor to a minimum as thedischarge pressure approaches a predetermined maximum discharge pressureand to increase the quantity of uid admitted to the compressor tomaximum as the discharge pressure decreases from the predeterminedmaximum discharge pressure toward the predetermined high dischargepressure.

15. In a motor driven fluid compressor unit, a governor to regulate thespeed of the motor having various speed setting positions between amaximum and a minimum speed setting position, a pressure device subjectto the discharge pressure of the compressor to control and graduallychange the speed setting position of the governor to the minimum speedposition as the discharge pressure of the compressor approaches a`predetermined high discharge pressure and to change -the governor to themaximum speed position as the discharge pressure decreases toward apredetermined minimum pressure, means to predetermine said high andminimum pressures, means to gradually reduce the quantity oi' fluidadmitted to the compressor to a minimum as the discharge pressureapproaches a. predetermined maximum pressure and to increase thequantity of iiuid admitted to the compressor to a maximum as thedischarge pressure approaches said predetermined high dischargepressure, and means to predetermine said high and maximum dischargepressures with respect to the last said means.

16. In a motor driven fluid compressor unit having a motor speedgovernor, a pressure responsive device for controlling and varyingprogressively and degressively the speed setting of the governor inaccordance with variations of the discharge pressure of the compressor,means to progressively and degressively unload and reload the compressorin accordance with the discharge pressure of the compressor above apredetermined high discharge pressure, and, means to prevent saidpressure responsive device from varying the speed setting of thegovernor when said predetermined high pressure is reached and unitil apredetermined minimum discharge pressure is reached.

11. Ina motor driven iiuid compressor unit having a motor speedgovernor, a pressure responsive device for controlling and progressivelyand degressively varying the speed 4setting of the governor inaccordance with the variations in the discharge pressure ,of thecompressor, means to progressively and degressively unload and reloadthe compressor in accordance with the discharge pressure below apredetermined 'compressor discharge pressure, means to render thepressure responsive device inoperative at said predetermined dischargeVpressure and operative thereafter at a predetermined minimum pressurelto vary the speed setting of the governor, and adjustable means toregulate the pressure range within which the last said means operates.

18. In a` motor driven fluid compressor unit having a motor speedgovernor, a pressure responsive device for controlling and progressivelyand degressively varying the speed setting of the governor in accordancewith the variations in the discharge pressure'oir the compressor, meansto progressively and degressively unload and reload the compressor inaccordance with the discharge pressure of the compressor above apredetermined pressure, adjustable means to predetermine the pressure atwhich the last said means operates,

means to render the pressure responsive device inoperative to vary thespeed setting of the governor at said predetermined'discharge pressureand thereafter render it operative at a predetermined minimum pressure,and adjustable means to regulate the pressure range within which thelast said means operates.

19. lIn a motor driven fluid compressor unit having a motor speedgovernor, a pressure responsive device i'or controlling andprogressively and degressively varying the speed setting or the governorin accordance with variations in the discharge pressure of thecompressor, means to progressively and degressively unload and reloadthe compressor in accordance with the discharge pressure of thecompressor above a predetermined pressure, adjustable means topredetermine thel pressure at which the last said means operates, andmeans to render the pressure responsive device inoperative to vary thespeed setting of the governor ata predetermined pressure not exceedingthe first said predetermined pressure and to maintain the pressureresponsive means inoperative thereafter until a predetermined lowdischarge pressure is reached.

20. In a motor driven fluid compressor unit having a motor speedgovernor, a pressure responsive device for controlling and progressivelyand degressively varying the speed setting of the governor in accordancewith variations in-the discharge pressure of the compressor, means toprogressively and degressively unload and reload the compressor inaccordance with variations in the discharge pressure of the compressorabove a predetermined pressure adapted to unload the compressorcompletely at a predetermined maximum discharge pressure, and means torender sasso the pressure responsive device inoperative to vary thespeed setting oi' the governor.

21. In a motor driven iiuid compressor uni having a motor speedgovernor, pressure responsive means to control and progressively anddegressively vary the speed setting oi. the governor in accordance withvariations oi the `discharge pressure o! the compressor, means toprogressive-4 compressor to control and progressively and de`,gressively vary the speed setting of the governor, means toprogressively and degressively unload and reload the compressor inaccordance with variations in the discharge pressure or the compressorabove a predetermined high pressure, and means to lock the rst saidmeans to render it inoperative to vary the speed setting ci the governorat said predetermined high pressure.

23. In a motor driven iluid compressor unit having a motor speedgovernor, a pressure responsive device for controlling and progressivelyand degressively varying the speed setting ot the governor in accordancewith variations in the discharge pressure of the compressor, means tounload the compressor progressively and degressively'above apredetermined high discharge pressure until a predetermined maximumdischarge pressure is reached and to vely and degressively reload thecompressor as the pressure falls from the predetermined maximum,discharge pressure until said predetermined high discharge pressure isreached, means to lock thevpressure responsive device to render itinoperative to vary the speed setting of the governor at saidpredetermined high discharge pressure to permit the governor to maintainthe motor at minimum speed and to unlock the pressure responsive deviceto permit the governor to accelerate the speed of the motor to a maximumwhen a predeter-4 mined lower discharge pressure is reached.

24. In a motor driven iiuid compressor unit 1 having a motor speedgovernorl a source of iluid,

means actuated by said iluid for controlling and progressively anddegressively varying the speed setting of the governor, means responsiveto the discharge pressure of the compressor to control actuation of thetlrst said means by said fluid, and means to progressively anddegressively unload and reload the compressor in accordance withvariations in the discharge pressure of the .compr-essor.

25. In a motor driven iiuid compressor unit having a source oi duid. amotor speed governor regulator comprising a chamber, means in thechamber actuatable by said nuid, means to vent the chamber and preventactuation of the last said means'by the nuid, means associated with themeans in the chamber to transmit movement thereof to the governor,pressure responsive means subject tothe discharge pressure of thecompressor, means controlled by the pressure responsive means to openand close the venting means, and means to unload and reload thecompressor above a predetermined high pressure comprising a casinghaving a chamber subject to the discharge pressure or thev compressor,movable means responsive to variations of the discharge pressure ot thecompressor, and a valve associated with the movable means to vary theamount of unloading and reloading of the compressor.

27. In a motor driven huid compressor unit ,having a source ci iluid, amotor speed governor regulator comprising movable means actuated by saidiiuid, means to prevent actuation of the movable means by said iluid,means associated with movable means to transmit movement thereof to thegovernor, pressure responsive means subject to the discharge pressureoi' the compressor, means controlled by the pressure responsive means torender the means to prevent actuation oi' the movable means operative,and means to unload and reload the compressor above a predetermined highpressure comprising means movable in response to variations in thedischarge' pressure of the compressor, and a valve associated with thelast said means to vary the amount of unloading and reloading of thecompressor in accordance with movements thereof.

28. In a motor driven fluid compressor unit having a motor speedgovernor, a pressure responsive device i'or controlling and varyingprogressively and degressively the speed setting of the governor inaccordance with variations of the discharge pressure of the compressor,means to progressively and degressively unload and re'- load thecompressor in accordance with the discharge pressure of the compressorabove a predetermined high discharge pressure comprising a casing havinga chamber subject to the discharge pressure of the compressor, movablemeans responsive to variations o! the discharge pressure of thecompressor, and a valve associated with the movable means to vary theamount ot unloading and reloading ofthe compressor.

29. In a motor driven iluid compressor unit having a motor speedgovernor, a pressure responsive device for controlling and varying-progressively and degressively the speed setting oi' the governor inaccordance with variations in the discharge pressure ot the compressor,means to. progressively and degressively unload and reload thecompressor in accordance with the discharge pressure of the compressorabove a predetermined high discharge pressure comprising movable meansresponsive to variations in the discharge pressure of the compressor,and a valve associated with the movable means and Vresponsive tomovements thereof to vary the amount of unloading and reloading thecompressor.

30. In a governor speed regulator for a motor driven compressorcomprising a casing having one chamber subjected to the dischargepressure oi' the compressor and a second chamber sub- Jected to intakemanifold pressure for the motor.

pressure responsive means in each chamber. means to transmit movement ofthe pressure responsive means in the second chamber to the governor,means to .admit atmosphere to the second chamber. and means actuated bythe pressure responsive means in the first said chamber to render thelast said means ineiective.

31. In a motor driven uid compressor, a governor to control the speed o!the motor, a pressure responsive device for controlling thecharacteristics of the governor in accordance with variations o! thedischarge pressure of the compressorl comprising a casing having achamber subject to the discharge pressure of the `compressor and asecond chamber subject tothe motor intake manifold pressure, pressureresponsive means in each chamber, means to vent the second chamber toatmosphere, means controlled by the pressure responsive means in thefirst said chamber to render the venting means ineffective upon apredetermined high discharge pressure until a predetermined minimumdischarge pressure is reached.

32. In a regulator for a motor driven fluid compressor having a governorand means to progressively and degressively unload and reload thecompressor in accordance with variations in the discharge pressure ofthe compressor, and a pressure responsive device to control the speedsetting of the governor in accordance with the variation or thedischarge pressure o! the compressor having chambers therein, means tovent one of the chambers to atmosphere, and.I means to close said ventwhen `the discharge pressure of the compressor reaches a predeterminedhigh pressure and maintain it closed until a predetermined minimumpressure ls reached.

33. In a regulator for a motor driven compressor having a governor, acasing having a chamber subject to the discharge pressure of thecompressor and a second chamber subject to the pressure oi the motorintake manifold, pressure responsive means in said chambers, ventingmeans for the second chamber, means associated vwith pressure responsivemeans in the other chamber to prevent venting by said venting means whenthe discharge pressure of the compressor reaches a predetermined highpressure and assure venting by said venting means when the dischargepressure of the compressor reaches a predetermined minimum dischargepressure, adjustable means to regulate the pressures at which said lastmeans operates, and means connected with the pressure responsive meansin said second chamber to directly control the governor speed setting. l

34. In a regulator for a motor. .drivenfiluid compressor having agovernor and a receiver to which the compressor discharges, comprising acasing having a chamber in communication with the receiver and a secondchamber in communication with the intake manifold oi the motor. aydiaphragm in the iirst said chamber, a bellows in said second chamber,a hollow plunger rod connected to the bellows, a vent formed in one endor the plunger.rod to open the rst said chamber to atmosphere, a plungerassociated with the diaphragm, a lever actuated by the plunger, a valveon said lever and controlled thereby to open and close the vent, aseries of levers connecting the hollow plunger rod and the governor tovary the speed setting thereof in accordance with the movements of thebellows, and means to predetermine the pressure at which the diaphragmmoves the plunger and lever to open and close the vent.

35. In a regulator for a motor driven fluid compressor having agovernor, comprising a casing having one chamber subject to thedischarge pressure o! the compressor and a second chamber subject to theintake manifold pressure o! the motor, a diaphragm in the first saidchamber movable upon variation in the compressor discharge pressure, aplunger connected with the diaphragm, a bellows in the second chamber, ahollow plunger connected to the bellows, an orifice in the hollowplunger to admit atmospheric air through the plunger to the chamber, apivotal lever associated with diaphragm plunger adapted to open andclose the vent upon variation of the discharge pressure of thecompressor, and a series of inter-connecting levers to connect thehollow plunger to the governor whereby the speed setting of the governormay be varied in accordance with the movement of the bellows, and meansto admit atmospheric air within the bellows whereby upon closing of thevent the vacuum created by the motor will expand the bellows andmaintain the governor at its minimum speed setting position and uponopening ot the vent the atmospheric pressure in the chamber willovercome the vacuum of the motor and compress the bellows to move the ngovernor to its maximum speed setting position.

(zr-mmm s. Bam

